Fluid-powered tools, particularly pneumatic tools, are used in a great variety of work applications. This invention relates primarily to pneumatic power tools, particularly of the type used as a clinching tool or blind rivet tool, such as disclosed in prior U.S. Pat. Nos. 3,430,539 and 3,457,763.
One of the problems with tools of the type disclosed in these prior art patents is adequate dispersal and delivery of aspirated lubricant mist to those pressure chambers of the tool which are successively more remote from the valved entry port of the air supply for the tool. There is a tendency for the atomized lubricant mist to precipitate out of its air carrier as it enters the first or nearest pressure chambers of the tool, thus substantially depleting the carrier of adequate lubricant content for the remaining chambers. The tendency for precipitation can be lessened by increasing the cross-sectional area of the entry port, but this increased input volume of pressurized air increases the rate of pressure buildup in the chambers and adversely affects the operating characteristics of the pistons and increases the retractive impact of the tool when the load on it is suddenly relieved, as in blind riveting.
The reference prior art structures use a manifold air distribution structure of uniformly-sized passageways and orifices for delivery of pressurized air to the several chambers. This results in a substantially simultaneous pressure buildup in all of the chambers, rather than a controlled differential buildup in the successive chambers for improved operating characteristics, decreased withdrawal impact of the tool, and better speed control.
The prior art structures also utilize coil spring biasing elements for restoring the pistons of the tool to load-engaging position after the pneumatic operating pressure is shut off. The operating pressure therefore has to be great enough not only to do the required work of the tool, but also to energize the compression coil spring.
All of the above present problems to which the improvements of the present invention are directed.